Denicotinizing process

ABSTRACT

A process for denicotinizing tobacco is disclosed in which tobacco, in an impregnating zone, is subjected to the action of a pool of an organic fluid which is a nicotine solvent and has a boiling point less than that of water. The fluid treated tobacco is then conveyed into an upper portion of the impregnating zone where it is contacted with the organic solvent fluid from which some of the nicotine has been removed. This solvent then drains down to the solvent pool at the lower portion of the impregnating zone. The tobacco is then contacted with a stream of hot gas whereby the excess fluid is vaporized and the tobacco expanded.

United States Patent Samuel 0. Jones;

[72] Inventors James Gilbert Ashburn; Grant M. Stewart; Glenn Philip Moser, all of Winston-Salem, N.C. [21] App1.No. 8,858 [22] Filed Feb. 5, 1970 [45] Patented Oct. 12, 1971 [73] Assignee R. J. Reynolds Tobacco Company Winston-Salem, N.C.

[54] DENICOTINIZING PROCESS 7 Claims, 1 Drawing Fig. 52 U.S. c1 131/143, 131/140 [51] Int. Cl ..A24b15/02, A24b 03/18 [50] FieldotSearch 131/17, 140-144 [56] References Cited UNITED STATES PATENTS 802,487 10/1905 Wimmer 131/143 Primary Examiner-Melvin D. Rein Attorney-Pencileton, Neuman, Williams & Anderson ABSTRACT: A process for denicotinizing tobacco is disclosed in which tobacco, in an impregnating zone, is subjected to the action of a pool of an organic fluid which is a nicotine solvent and has a boiling point less than that of water. The fluid treated tobacco is then conveyed into an upper portion of the impregnating zone where it is contacted with the organic solvent fluid from which some of the nicotine has been removed. This solvent then drains down to the solvent pool at the lower portion of the impregnating zone. The tobacco is then contacted with a stream of hot gas whereby the excess fluid is vaporized and the tobacco expanded.

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HEIONVdXB QIQQQ ams DENICOTINIZING PROCESS This invention relates to a process for denicotinizing tobacco and has for an object the provision of a denicotinizing process which results in a tobacco which can readily be used in the manufacture of cigarettes and other smoking articles without special treatment.

A number of procedures have been. suggested in' the prior art for removing nicotine from tobacco. Such processes include treatment of the tobacco with ammonia or with steam at elevated temperatures. Many of these procedures have not been entirely satisfactory, particularlyas applied to flue-cured tobacco, since the treatment conditions effective for nicotine removal may be so severe that the flavor and aroma of the tobacco undergoing treatment are adversely affected. Prior art procedures have also been proposed for extracting nicotine fromtobacco by the use of nonaqueous organic liquids. While these processes may be very effective to extract the nicotine, the resulting tobacco is usually gummy in nature and is very difficult to handle in the manipulative steps that are subsequently required to form a desired end product.

Accordingly, it is a further object of this invention to provide a process for denicotinizing tobacco bythe use of an or-' ganic liquid solvent for the nicotine under process conditions which result in a tobacco product that may. readily be employed in the manufacture of cigarettes and other smoking articles.

A further object of this invention is theprovision of a denicotinizing process which is effective to remove nicotine from tobacco without the net removal of desired flavor and aroma-producing substances.

A still further object of this inventionis the provision of a continuous denicotinizing process that may be readily applied to all types of tobacco and particularly flue-cured tobacco to effectively remove the nicotine without adversely affecting-the smoking qualities of the product. I

Further and additional objects will appear from the following description, the accompanying drawing, and the appended claims.

In accordance with one embodiment of this invention, a process is provided in which tobacco is impregnated in an im pregnation zone with a low boiling organic liquid solvent'for nicotine, said liquid solvent having a boiling point less than that of water at atmospheric pressure. The solvent containing extracted nicotine and certain tobacco flavor and aromaproducing chemicals is withdrawn from the impregnating zone and treated in a suitable manner selectively to remove the nicotine. The solvent still containing most, if not all, of the flavor and aroma-producing substances is then recycled to the tobacco impregnating zone so that after an initial period of operation in a continuous process there is little or no net lossof flavorants or aroma-producing substances in theprocess. The tobacco which has been extracted but while still wet or moist with solvent is separately withdrawn from the impregnating zone and immediately contacted with a gas which has been heated to a temperature of at least about 30 F. above the boiling point of the solvent at the gas-contacting pressure. Under these conditions the solvent in the treated tobacco rapidly vaporizes causing it to expand. The expanded tobacco product is free of the gummy properties that are usually observed when tobacco is denicotinized by organic solvent procedures as suggested in the prior art and may be readily subjected to subsequent treatment necessary for the manufacture of cigarettes or other smoking articles.

. The tobacco treated in accordance with the process of this invention may be in the form of shreds, strips, leaves or stems. Any type of tobacco is suitable and the invention is useful for the processing of burley and oriental tobaccos. The invention has particular utility in the treatment of flue-cured tobacco. in any event, it is preferred that the process be carried out with shredded tobacco since in that form the tobacco is relatively easy to handle in continuous procedures and the final product of the process need not be subjectedto shredding as may be required for cigarette manufacture. In other words, shredded tobacco may be charged to the process of this invention and further shredding or cutting is not required on the product discharged from the process. The moisture content of the tobacco charged to the process is preferably within the range of about 5 to about 200 percent by weight (dry basis). The moisture may be applied, if necessary, in any desired manner such as by spraying, wet steam treatment, or other wise, as will be obvious to one skilled in the art.

The organic liquid employed for impregnating and extracting the tobacco is one which is a solvent for nicotine and is chemically inert to the tobacco being treated. It has a boiling point less than that of water at atmospheric pressure but at the same time the boiling point is sufficiently high so that it may readily be maintained in the liquefied condition at the pressures existing n the tobacco impregnation and extraction zone. Suitable organic liquids are the aromatic hydrocarbons such as benzene; the ethers such as methylethyl ether, diethyl ether,

diis'opropyl ether and methylbutyl ether; the esters such as methyl acetate, ethyl acetate and methyl propionate; the

aliphatic hydrocarbons such as pentane, isopentane, 2,2- dimethylbutane, 2,3-dimethylbutane, and hexane; the cyclo aliphatic hydrocarbons such as cyclobutane; the halogenated substituted aliphatic hydrocarbons such as ethyl chloride, propyl chloride, isopropyl chloride, butyl chloride, sec-butyl chloride, tert-butyl bromide, methylene chloride, chloroform, carbon tetrachloride, ethylene dichloride, and ethylidene dichloride; and the fluorinated hydrocarbons generally known as Freons such as trichloromonofluroremethane and trichlorotrifluoroethane. Mixtures of the several solvents may be used and if so, such mixtures are preferably azeotropic in nature. The preferred impregnating organic liquid is one which is noninflammable, and partly for this reason the Freons have been found to be particularly satisfactory.

It is preferred that the impregnation of the tobacco be carried out by continuous method. This may be achieved by continuously passing a stream of tobacco into a pool of the organic solvent under extracting conditions. With the lower boiling solvents, this pool may be maintained under superatmospheric pressure and at a moderately elevated temperature so that thorough impregnation of the tobacco and extraction of nicotine from the tobacco readily occurs. The tobacco is then moved out of the pool, preferably by a suitable conveyor, and is then discharged from the impregnation zone, at which time the percent ofsolvent in the tobacco is in excess of about 5 percent by weight and preferably in excess of about 25 percent by weight in order to effect the desired expansion. The tobacco while still wet or moistened with the solvent is then immediately subjected to a stream of hot gas which serves the dual function of removing the solvent from the tobacco and of causing the tobacco to expand so that it has a dry fluffy nature which will enable it to be reordered to the desired moisture content, if necessary, and readily used in the manufacture of smoking articles such as cigarettes. In order to obtain the desired expansion and solvent removal, it is preferred that the gas contacted with the impregnated tobacco at this stage have a temperature at least about 30 F. above the boiling point of the impregnating liquid, suitably in the range of about 250 to 400 F. when a liquid having a boiling point less than about l F. is employed. The pressure in the hot gas contacting zone is not greater than that existing in the impregnating zone and the temperature of the hot gas should be sufiiciently high in order to pennit the desired vapor removal and expansion to take place within the tobacco. Excessive temperatures are avoided since they may have an adverse effect on the smoking quality of the tobacco.

in order to separate the nicotine from the tobacco, a portion of the solvent liq'uid enriched in nicotine is withdrawn from the pool of organic fluid in the impregnation zone. This withdrawn liquid is subjected to a nicotine separating step whereby at least a portion of the nicotine is removed and the liquid is recycled to the impregnating zone. It is preferred that the separation step be selective for nicotine so that significant amounts of the flavor and aroma-producing substances which are desired in the tobacco will be left in the solvent for reincorporation in the tobacco when the nicotine-lean solvent liquid is recycled to the impregnating zone.

Any desired means may be employed to remove nicotine from the liquid withdrawn from the impregnation zone. This may be effected by known means such as dialysis, contact with ion exchange resins or the use of known nicotine precipitants such as tannic acid, picric acid, molybdic acid, tungstic acid, compounds of heavy metals, etc. However, in accordance with one embodiment of this invention, it is preferred that the nicotine be removed from the solvent be treating the nicotinerich solvent with an acid-reacting aqueous solution. In such case the solvent containing the dissolved nicotine should be essentially immiscible with water so that upon contact of the organic liquid solution with the acidic aqueous solution the nicotine in the form of its acid salt will pass into the aqueous phase, as is well known in the art. Thereafter the organic sol vent, essentially free of nicotine, is recycled to the initial tobacco impregnating step. inasmuch as the flavorants and aromas are usually quite soluble in the organic liquid but less so in water, they will also be returned to the tobacco impregnation zone. Accordingly, after an initial period of operation of the process, the concentration of the flavorants and aromas builds up in the liquid being recycled so that there is no appreciable net extraction of these components and it is essentially only the nicotine and other related alkaloids that are separated from the tobacco,

For a more complete understanding of this invention, reference will now be made to the accompanying drawing which in diagrammatic from illustrates an apparatus for carrying out the process of this invention. In this embodiment shredded flue-cured tobacco is passed by means of a conveyor to a moistener 12 in which the moisture content of the tobacco, if necessary, is adjusted to between about and 30 percent by weight dry basis. Suitably the moisture content is adjusted to 13 to 20 percent by weight. Under certain conditions of plant operation, the moisture content of the tobacco may already fall within the desired range and, accordingly, the tobacco charged to the process may bypass the moistener 12 by a conveyor 14 if desired. The moistened tobacco from the moistener 12 or the bypass conveyor 14 or a confluence of both passes to a rotary star valve l6 via conduit 18. The star valve serves to discharge the tobacco at a prescribed rate into the lower portion of an elongated impregnator 20.

The impregnator 20 is inclined at an angle to the horizontal (preferably at about 15) and is provided with a motor driven screw conveyor 22 by which the tobacco is moved from the lower portion of the interior of the impregnator to the upper portion thereof. The rotary star valve 16 prevents pressure release during the introduction of tobacco into the impregnator thereby permitting a suitable pressure to be maintained within the impregnator. The selected organic liquid impregnating fluid is introduced into the lower portion of the impregnator via conduit 24. The impregnator is provided with an external jacket for receiving a heat exchange medium whereby the temperature of the tobacco and impregnating fluid moving into and through the impregnator ma be controlled and, if desired, similar heat-exchange means (not shown) may be provided in the shaft of the screw conveyor 22. The heat-exchange means supplies heat to facilitate impregnation of solvent into the tobacco. Heat is also supplied to the upper section of the impregnator thereby preventing condensation in that portion of the equipment. A pressure-equalizing line 18a is provided between the vapor space in the impregnator and the discharge conduit from the star valve 16.

At the upper portion of the impregnator 20, there is provided a discharge conduit 26, a pressure release rotary star valve 28, and a conduit 30 which serves to discharge the impregnated tobacco directly into a stream of hot gas circulating through a conduit 32 and a vertical expander 34 of enlarged cross section to a tobacco separator 36 which may take the form of a conventional cyclone separator. The rotary star valve 28 is arranged to discharge the tobacco from the impregnator without materially affecting the superatmospheric pressure maintained therein.

The expanded tobacco is discharged from the bottom of the separator 36 through a conveyor 38 to a steam stripper 40 in which any residual organic fluid is separated from the tobacco and conveyed through line 42 to a conventional organic liquid recovery unit 44. Tobacco from the stripper 40 is moved by conveyor 46 to a reorderer 48 from which the final expanded tobacco product is discharged through a conveyor 50. In the reorderer, sufficient water and sometimes flavoring and dressing materials are added to provide the flnal desired product.

Water and air are withdrawn through lines 52 and 54 from the organic liquid recovery unit 44 and fresh organic liquid is fed to the unit through conduit 56. A level control valve 58 is provided in line 24 to regulate the flow of organic liquid to the impregnator 20 in response to the level 60 of the pool or body 62 of the organic liquid maintained in the lower portion of the impregnator.

The hot gases from which the tobacco has been separated is recycled from the top of the separator 36 via conduit 64, heater 66 and fan 68 to conduit 32. Excess vapors of the organic liquid which tend to accumulate in the expansion system are diverted in a stream through line 70 to the recovery system 44.

Nicotine enriched solvent is withdrawn from the impregnator 20 through valved line 72, an orifice mixer 74 and line 76 to a liquid separator 78. Dilute acid stored in tank 80 flows through valved line 82 to the mixer 74 in which the nicotinerich organic liquid is thoroughly mixed with the acid solution before flowing to the liquid separator 78. Aqueous acid containing the extracted nicotine in the form of its acid salt is discharged from liquid separator 78 through valved line 84. Solvent lean in nicotine is recycled to the upper portion of the impregnator 20 through valved line 86, pump 88, and valved line 90. Additional makeup liquid may be supplied to line from a makeup tank 92 which may serve as a surge tank, if desired. A valved recycle line 94 for the liquid separator 78 is also provided.

The preferred organic liquid for use in accordance with this invention is trichloromonofluoromethane (i.e., Freon-l 1) having an atmospheric pressure boiling temperature of approximately 74 F. When this solvent is utilized the tobacco having the appropriate moisture content is passed into the impregnator 20 through the rotary valve 16. The liquid level in the impregnator is maintained during operation by passing additional fluid to the impregnator through conduit 90 or through conduit 24 in response to the liquid level control valve 58. Heating fluid is passed to the jacket of the impregnator 20 to maintain the desired temperature within the impregnator. Under these conditions the Freon vapors generate a superatmospheric pressure which is necessary to maintain the body or pool 62 of liquid in the lower portion of the impregnator. The tobacco having been introduced underneath the surface of the organic liquid is thoroughly wetted" and then elevated by the screw conveyor toward the upper portion of the impregnating zone. During this process a portion of the nicotine is extracted from the tobacco and the tobacco emerges from beneath the surface of the liquid and progresses upwardly through an atmosphere of saturated vapor. Any excess liquid containing additional extracted nicotine drains back to the pool 62. As the tobacco progresses upwardly through the impregnator under superatmospheric pressure through the saturated vapor atmosphere, impregnation of the tobacco continues to occur until it is essentially complete at the time that it reaches the upper portion of the impregnator. Thereafter the tobacco still containing a significant amount of impregnating fluid (i.e., greater than about 5 percent, preferably greater than about 25 percent, by weight) is discharged through conduit 26 and the rotary valve 28 to conduit 30 wherein the pressure is reduced to about atmospheric and it is then passed immediately into a rapidly moving stream of hot gases heated to a temperature substantially above the boiling point of the organic liquid, suitably between about 250 and 400 F., for example, 310 F. and at a pressure less than that existing in the impregnator. The tobacco suspended in the hot gases passes upwardly through the vertical expander 34 in which the tobacco is expanded by vaporization of the liquid. The tobacco is then separated from the vapors in the separator 36. The separated gas comprising a mixture of air, water vapor and Freon vapor is then recycled through heater 66 and forced by fan 68 into contact with a fresh charge of impregnated tobacco from conduit 30. A portion of the vapor is recycled from line 64 through line 70 to the liquid recovery system 44 in order to compensate, at least in part, for organic liquid introduced with the tobacco into the expander 34.

In order to effect denicotinization of the tobacco, a stream of nicotine-rich solvent liquid is withdrawn while hot from pool 62 through line 72 to liquid separator 78. A stream of dilute acid (e.g., 1 percent aqueous sulfuric acid) is passed from makeup acid tank 80 to the orifice mixer 74, where it thoroughly intermixes with the solvent in line 76 prior to discharge into the separator 78. This separator is of conventional construction and permits the separation of the relatively immiscible liquids into an aqueous layer and an organic liquid layer. In the embodiment shown where Freon-ll is the solvent, which has a higher specific gravity than the aqueous solution, the Freon stratifies in the lower portion of the separator 78. The Freon, essentially free of nicotine but containing extracted tobacco flavorants, is withdrawn through valved line 86 and recycled to the upper portion of the impregnator 20, wherein it flows downwardly through the ascending stream of tobacco back to the pool 62. The aqueous acid solution containing the nicotine in the form of its watersoluble acid salt is withdrawn from an upper portion of the separator 78 through the valved line 84.

in one example of a continuous process utilizing the apparatus previously described, shredded tobacco was continuously fed into the impregnator 20 at an average rate of about 609 grams per minute. The tobacco constituted the shreds of flue-cured overripe tip leaves having a nicotine content of about 3.98 percent by weight and a moisture content of about 17 percent by weight. The impregnator was operated at 40 p.s.i.g. The impregnating solvent was Freon-l 1 and was withdrawn hot (at about 147 F.) from the pool 62 through line 72 at the rate of 3 gallons per minute. Dilute aqueous sulfuric acid (0.9 percent 11,80 by weight) at the rate of 0.4 gallons per minute was mixed with the Freon in the orifice mixer 74 and passed to the liquid separator 78. The Freon which was essentially free of nicotine was recycled to the upper section of the impregnator and the acid solution containing the nicotine which stratified in the upper portion of the liquid separator 78 was periodically withdrawn through line 84. The tobacco discharged from the separator 36 had a nicotine content of L76 percent by weight (representing a 56 percent reduction) and after stripping and reordering was suitable for the manufacture of cigarettes.

Comparable results have been obtained when dilute aqueous solutions of malic and citric acids have been used to selectively remove the nicotine from the Freon. Other acids may be used for the purpose and include any aqueous acid solutions in which the pH of the aqueous layer during separation is less than about 6 and preferably below about 5 The product of the process is essentially free of compressed laminated tobacco particles which are found incident to the initial shredding of the tobacco used as a charge stock. The

product may be used to manufacture cigarettes in the conventional manner or it may be mixed with other tobaccos to provide a desired blend for use in the manufacture of cigarettes or other smoking articles.

While a particular embodiment of this invention has been described in the foregoing, it will of course be apparent that other modifications may be made without departing from the spirit and scope of the appended claims.

What is claimed is: l. A process of denicotinizing tobacco which comprises maintaining a tobacco impregnating zone containing an organic fluid which in the liquid state is a solvent for nicotine, said fluid having a boiling point less than that of water at atmospheric pressure and forming a pool of liquid in a lower portion of said zone and an atmosphere of vapor in an upper portion thereof, passing nicotine-containing tobacco into contact with said liquid pool in said lower portion, then conveying the resulting liquid treated tobacco into said upper portion, withdrawing the tobacco impregnated with said fluid from said upper portion, then contacting the withdrawn impregnated tobacco with a stream of hot gas whereby to vaporize the fluid and expand the tobacco, separately withdrawing liquid containing dissolved nicotine from said pool, separating nicotine from the separately withdrawn liquid, and introducing the resulting nicotine-depleted liquid into contact with said tobacco in said upper portion for downward flow through said tobacco to said pool.

2. The process of claim 1 wherein said liquid is essentially immiscible with water and wherein the nicotine separation step is effected by contacting the separately withdrawn liquid with an aqueous acid solution into which the nicotine selectively dissolves.

3. The process of claim 2 in which the organic fluid comprises a fluorohydrocarbon having a boiling point at atmospheric pressure of less than about F.

4. The process of claim 3 wherein the organic fluid also contains an alcohol or a ketone having a boiling point at atmospheric pressure of less than about 212 F.

5. The process of claim 3 wherein said fluid is trichloromonofluoromethane.

6. The process of claim 2 wherein said tobacco is shredded tobacco.

7. A process of denicotinizing and increasing the filling capacity of tobacco which comprises maintaining a tobacco impregnating zone containing an organic fluid which in the liquid state is a solvent for nicotine, said fluid having a boiling point less than that of water at atmospheric pressure and forming a pool of liquid in a lower portion of said zone and an atmosphere of vapor in an upper portion thereof, introducing a stream of nicotine-containing tobacco beneath the surface of said pool, conveying said tobacco stream upwardly from said pool into the vapor atmosphere in said upper portion of said zone, withdrawing said tobacco stream impregnated with said fluid from said upper portion, contacting the withdrawn tobacco stream with a stream of hot gas whereby to vaporize the fluid and expand the tobacco, separately withdrawing a stream of liquid containing dissolved nicotine from said pool, separating nicotine from the separately withdrawn liquid, introducing a stream of the resulting nicotine-depleted liquid into contact with said tobacco stream moving upwardly in the upper portion of said zone, and flowing said introduced nicotine-depleted fluid stream downwardly in said zone to said pool in contact with the upwardly moving tobacco stream.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,612,066 Dated October 12, 1971 Samuel 0. Jones; James Gilbert Ashburn; ln nt fl Grant M. Stewart; and Glenn Philip Moser It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 18, "very" should be: guite Column 2, line 7, "other wise" should be: otherwise 2, line 12, after "pressure" insert: and Eeferably less than abou t l80 F. at atmospheric pressure 2, line 28, "trichloromonofluroremethane" should be:

trichloromonofluoromethane Column 3, line 11, "be" (2nd occurrence) should be: 131

" 3, line 57, "ma" should be: may

Signed and sealed this 11th day of April 1972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

2. The process of claim 1 wherein said liquid is essentially immiscible with water and wherein the nicotine separation step is effected by contacting the separately withdrawn liquid with an aqueous acid solution into which the nicotine selectively dissolves.
 3. The process of claim 2 in which the organic fluid comprises a fluorohydrocarbon having a boiling point at atmospheric pressure of less than about 180* F.
 4. The process of claim 3 wherein the organic fluid also contains an alcohol or a ketone having a boiling point at atmospheric pressure of less than about 212* F.
 5. The process of claim 3 wherein said fluid is trichloromonofluoromethane.
 6. The process of claim 2 wherein said tobacco is shredded tobacco.
 7. A process of denicotinizing and increasing the filling capacity of tobacco which comprises maintaining a tobacco impregnating zone containing an organic fluid which in the liquid state is a solvent for nicotine, said fluid having a boiling point less than that of water at atmospheric pressure and forming a pool of liquid in a lower portion of said zone and an atmosphere of vapor in an upper portion thereof, introducing a stream of nicotine-containing tobacco beneath the surface of said pool, conveying said tobacco stream upwardly from said pool into the vapor atmosphere in said upper portion of said zone, withdrawing said tobacco stream impregnated with said fluid from said upper portion, contacting the withdrawn tobacco stream with a stream of hot gas whereby to vaporize the fluid and expand the tobacco, separately withdrawing a stream of liquid containing dissolved nicotine from said pool, separating nicotine from the separately withdrawn liquid, introducing a stream of the resulting nicotine-depleted liquid into contact with said tobacco stream moving upwardly in the upper portion of said zone, and flowing said introduced nicotine-depleted fluid stream downwardly in said zone to said pool in contact with the upwardly moving tobacco stream. 